1. Field of the Invention
The invention relates to the field of lithium ion battery technology, and more particularly to a lithium ion battery.
2. Description of the Related Art
Conventionally, a cylindrical lithium ion battery generally uses rigid packaging materials, such as stainless steel, to form a metal shell for containing the battery core, and a rubber seal is used to confine the battery core in the shell by sealing the opening of the shell. Since lithium ion batteries are likely to produce gas in the case of damage, overcharge, and high temperature, a gas outlet is commonly arranged at an anode head thereof to avoid explosion caused by delaying gas release, which makes structures of the anode end of the battery complicated. In some other cases, a pressure relief valve is disposed in the bottom end wall of the metal shell. However, the pressure relief valve disposed in the bottom end wall of the metal shell is covered with a positive terminal, which somehow delays gas release when the pressure in the battery is above a certain threshold.
In addition, the anode of a conventional cylindrical lithium ion battery is usually a protruded head and the cathode thereof is a flat bottom, and the anode and cathode of a conventional lithium battery are disposed on two different ends. In use, cylindrical lithium ion batteries are often connected in series to provide high capacity and high power of voltage and current for electrical appliances. If they are connected in parallel, a dedicated battery box is required. Thus, it is troublesome and difficult to meet varied requirements under different occasions either in series or in parallel.
In addition, for sealing and confining the battery assembly including the battery core, the metal shell, and the rubber seal, a cover is conventionally formed over the cylindrical side wall of the metal shell, the peripheral edge of the bottom end wall of the metal shell, and the peripheral edge of the top surface of the rubber seal; or a cap is formed over the top surface of the rubber seal and the top portion of the cylindrical side wall of the metal shell. To have the required sealing effect, the cover must be appropriately compressed to decrease the air clearance between the cover and the surfaces it covers in addition to being appropriately compressed to conform to the surfaces it covers. To reach the required sealing effect and to stably confine the battery assembly, the cap must be welded to top portion of the cylindrical side wall of the metal shell and must be appropriately compressed to decrease the air clearance between the cap and the surfaces it covers in addition to being appropriately compressed to conform to the surfaces it covers. Thus, the sealing effect of the conventional sealing structures for the battery is inadequate because space always exists between the cover (or cap) and the surfaces it covers. Besides, the processes for constructing the conventional sealing structures are complicated and demanding so that the production cost of the battery is high.